Thermodynamic parameters for the complexation of Tc(IV) species with chloride under aqueous conditions

Technetium-99 (99Tc) is found in aqueous environmental systems (due to nuclear testing, reprocessing, and accidents), where it can coexist with halides. While Tc(VII) is the primary oxidation state under oxic conditions, Tc(IV) can also be present in the environment. Accurate knowledge of the complexation of Tc(IV) species with Cl– improves understanding of Tc behavior in the environment. Results of batch solvent extraction experiments indicate that a single chloride complex is formed in solution from an exothermic reaction with a negative entropy. Computational results support classifying an outer-sphere complex between the Tc(IV) species and chloride.